1. Field of the Invention
The present invention relates to a system and method for providing security for a wireless network, such as an ad-hoc wireless communications network, based on the position information relating to mobile nodes. More particularly, the present invention relates to a system and method for trusted infrastructure devices to compute the location of a mobile node in a wireless communications network, such as an ad-hoc terrestrial wireless communications network, during the authentication process.
2. Description of the Related Art
Wireless communications networks, such as mobile wireless telephone networks, have become increasingly prevalent over the past decade. These wireless communications networks are commonly referred to as “cellular networks” because the network infrastructure is arranged to divide the service area into a plurality of regions called “cells”.
Specifically, a terrestrial cellular network includes a plurality of interconnected base stations that are distributed geographically at designated locations throughout the service area. Each base station includes one or more transceivers that are capable of transmitting and receiving electromagnetic signals, such as radio frequency (RF) communications signals, to and from user nodes, such as wireless telephones, located within the base station coverage area. The communications signals include, for example, voice data that has been modulated according to a desired modulation technique and transmitted as data packets. As can be appreciated by one skilled in the art, the transceiver and user nodes transmit and receive such data packets in multiplexed format, such as time-division multiple access (TDMA) format, code-division multiple access (CDMA) format, or frequency-division multiple access (FDMA) format, which enables a single transceiver at the base station to communicate simultaneously with several user nodes in it's coverage area.
In recent years, a type of mobile communications network known as an “ad-hoc” network has been developed for use by the military. In this type of network, each user node is capable of operating as a base station or router for the other user nodes, thus eliminating the need for a fixed infrastructure of base stations. Details of an ad-hoc network are set forth in U.S. Pat. No. 5,943,322 to Mayor, the entire content of which is incorporated herein by reference.
More sophisticated ad-hoc networks are also being developed which, in addition to enabling user nodes to communicate with each other as in a conventional ad-hoc network, further enable the user nodes to access a fixed network and thus communicate with other user nodes, such as those on the public switched telephone network (PSTN), and on other networks such as the Internet. Details of these types of ad-hoc networks are described in U.S. patent application Ser. No. 09/897,790 entitled “Ad Hoc Peer-to-Peer Mobile Radio Access System Interfaced to the PSTN and Cellular Networks”, filed on Jun. 29, 2001, and in U.S. patent application Ser. No. 09/815,157 entitled “Time Division Protocol for an Ad-Hoc, Peer-to-Peer Radio Network Having Coordinating Channel Access to Shared Parallel Data Channels with Separate Reservation Channel”, filed on Mar. 22, 2001, now U.S. Pat. No. 6,807,165, the entire content of each being incorporated herein by reference.
In either conventional wireless communications networks, or in ad-hoc wireless communications networks, it may be necessary or desirable to know or determine the geographic location of user nodes. Different types of location determining services and techniques for wireless communications networks are described in a publication by Nokia which can be found on the Nokia website at “www.nokia.com/press/background/pdf/mlbs.pdf”, the entire content of which being incorporated herein by reference. In particular, the Nokia document states that location identification services are currently provided in wireless communications networks based on three major technologies. One of these technologies uses cell identification combined with Round Trip Time (RTT), Timing Advance (TA) and Measured Signal level (RX level), Time Difference of Arrival (TDOA) and Angle Of Arrival (AOA) techniques, the details of which can be appreciated by one skilled in the art. A second technology uses cellular signal timing based methods for code division multiple access (CDMA) and wideband code division multiple access (WCDMA). The third technology described in the Nokia document employs Global Positioning System (GPS) techniques.
Another list of methods and techniques currently used in the wireless communications industry for providing location services can be found at “www.911dispatch.com/911_file/location_tech.html”, the entire content of which being incorporated herein by reference. Although the GPS technique is the last technique mentioned in this list, it is generally viewed as being more accurate than all of the other methods. Further details and descriptions of GPS based methods are set forth in a publication by J. J. Spilker Jr. entitled “Satellite Constellation and Geometric Dilution of Precision”, in a publication by P. Axelrad et al. entitled “GPS Navigation Algorithms”, in a publication by Bradford W. Parkinson entitled “GPS Error Analysis”, and in a publication by N. Ashby et al. Entitled “Introduction to Relativistic Effects on the Global Positioning System”, each found in “GPS—Theory and Applications”, American Institute of Astronautics, 1996, the entire content of each being incorporated herein by reference.
Despite the fact that the GPS technique has been in use for a considerable period of time and most of the world's navigation relies on this technique, the GPS technique is very susceptible to errors in measurement. Therefore, the GPS technique is capable of providing location determination results with very high accuracy only after performing a relatively large number of measurements to remove such errors. A description of the shortcomings of GPS is set forth in a document by IMA entitled “Mathematical Challenges in Global Positioning Systems (GPS)” which can be found at “www.ima.umn.edu/gps”, the entire content of this document being incorporated herein by reference. Certain other tests also demonstrate that the GPS technique is unsuitable for terrestrial-based networks.
In addition, other methods and techniques which do not use GPS satellites for determining mobile station locations in a wireless communications network typically require that the signal from the mobile station be received by at least two cell sites that can measure and process the delay between signal arrivals, identify the direction of the signal based on “path signature”, and determine the distance between mobile station and the cell towers. In all of these methods, information processing is executed in a designated central processing unit (CPU) which is typically located at a cell tower next to the base station (BTS). Also, most of these methods were designed to comply with E911 requirements without requiring that excessive modifications be made to existing wireless communications systems. Examples of other location determining techniques are set forth in a document by CERN—European Organization for Nuclear Research, which can be found at “rkb.home.cern.ch/rkb/ANI16 pp/node98.html#SECTION00098000000000000000”, in a document by Wendy J Woodbury Straight entitled “Exploring a New Reference System”, which can be found at “menstorsoftwareince.com/profile/newref.html”, and in a document entitled “An Introduction to SnapTrac Server-Aided GPS Technology”, which can be found at “www.snaptrack.com/pdf/ion.pdf”, the entire content of each being incorporated herein by reference. Additional details may also be found in U.S. patent application Ser. No. 09/988,001 entitled “A System and Method for Computing the Location of a Mobile Terminal in a Wireless Communications Network”, filed on Nov. 16, 2001, now U.S. Pat. No. 6,728,545, which describes a system and method for determining location with the use of technologies such as GPS, the entire content being incorporated herein by reference.
Accordingly, a need exists for a system and method for determining the location of a mobile user node in a wireless communications network by trusted infrastructure devices to determine if the device is physically within a predetermined “safe zone”, and provide access to the network based on this location determination.